[REF] base_vat: Speed-up check_vat if there is not vat

The following line of code:

    self.env.ref("base.europe").with_context(lang="fr_CA").country_ids

It is executing the following query:

    SELECT res_country_res_country_group_rel.res_country_group_id, res_country_res_country_group_rel.res_country_id FROM res_country_res_country_group_rel, "res_country" LEFT JOIN "ir_translation" AS "res_country__name" ON ("res_country"."id" = "res_country__name"."res_id" AND "res_country__name"."type" = 'model' AND "res_country__name"."name" = 'res.country,name' AND "res_country__name"."lang" = 'fr_CA' AND "res_country__name"."value" != '')
    WHERE 1=1 AND res_country_res_country_group_rel.res_country_group_id IN (1) AND res_country_res_country_group_rel.res_country_id = res_country.id
    ORDER BY COALESCE("res_country__name"."value", "res_country"."name")
    OFFSET 0

With duration: 138.119ms

But it is not needed to spend processing to compute it if it even will not be used if the `vat` is empty

If your website checkout process is creating almost the partners without `vat`
it could have a better performance

closes odoo/odoo#85064

Signed-off-by: Olivier Colson <oco@odoo.com>

addons/base_vat/models/res_partner.py

@@ -149,14 +149,15 @@ class ResPartner(models.Model):
         # This is for API pushes from external platforms where you have no control over VAT numbers.
         if self.env.context.get('no_vat_validation'):
             return
+        partners_with_vat = self.filtered('vat')
+        if not partners_with_vat:
+            return
         if self.env.context.get('company_id'):
             company = self.env['res.company'].browse(self.env.context['company_id'])
         else:
             company = self.env.company
         eu_countries = self.env.ref('base.europe').country_ids
-        for partner in self:
-            if not partner.vat:
-                continue
+        for partner in partners_with_vat:
             is_eu_country = partner.commercial_partner_id.country_id in eu_countries
             if company.vat_check_vies and is_eu_country and partner.is_company:
                 # force full VIES online check